Modelling and analysis of hydraulic wind turbines with integrated energy storage

Abstract

In the present work, a refrigeration cycle model is developed to quantify the benefits of using deep seawater from below the thermocline. The model showed a Coefficient Of Performance (COP) improvement of 37.5% when using deep seawater instead of surface seawater. It also showed that the integration of an energy storage device into the hydraulic wind turbine allows it to provide a more consistent supply of cold deep seawater. This results in the refrigeration cycle providing more stable delivery temperatures and a marginal increase in COP. When the hydraulic wind turbine operates in higher wind climates, it was also observed that mixing some surface seawater to compensate for deficits in the wind-driven deep seawater flow is not significantly detrimental to the system performance. In lower wind scenarios, the mixing process can have a more negative effect on the COP. Nonetheless, it is still higher than that observed in coastal systems operating on only surface seawater. Overall, the electrical energy saving resulting from the use of cold deep seawater adds around 7% to the hydraulic wind farm yield. This more than compensates for the higher transmission losses associated with hydraulic wind turbines.